Flexible pipe coupling

FIELD OF THE INVENTION

0001This invention concerns mechanical pipe couplings for joining pipes together, and especially couplings allowing axial, torsional and angular flexibility between the pipes.

BACKGROUND OF THE INVENTION

0002Piping networks for conveying fluids (liquids, gases, powders, slurries, sludges and the like) are used in a wide spectrum of industries including the petroleum industry, the chemical industry, mining, construction, manufacturing, as well as in municipal water service. It is advantageous to assemble piping networks using pipe segments sealingly joined to one another with mechanical fittings. Mechanical fittings typically comprise couplings that engage the pipe ends and are held together by removable fasteners.

0003Mechanical fittings are advantageous because they avoid the use of open flame or electrical arc, as required in welding, to effect a fluid tight joint between pipe ends. The assembly of mechanical fittings requires less skill than welded or brazed joints, and they are, therefore, less expensive to fabricate. Mechanical fittings also provide greater versatility for modification or repair of the piping network since repairs can be effected or new sections can be added by simply unbolting existing couplings and making the new connections as desired.

0004A problem common to all piping networks, regardless of how the pipes are connected, is the lack of joint flexibility axially (lengthwise along the pipe), torsionally (rotation about the long axis of the pipe) and angularly (the relative angle between one pipe and another to which it is connected). Rigid joints mean that the tolerances to which the pipes are cut and the angles at which they are joined must be maintained within relatively close limits so that the piping network will fit together as designed, without significant deviation from the plan. It is expensive and not always possible to maintain the necessary tight tolerances on pipe lengths, especially when the networks are assembled in the field as opposed to in a workshop where conditions for cutting and assembly are under greater control.

0005Flexible pipe joints are also advantageous for piping networks that must expand or contract and yet maintain fluid-tight connections. In one example, a piping network for the pneumatic transport of pulverized coal from the coal crushing station to the furnace in a power plant must have enough flexibility to maintain its connection to the furnace, which expands in size when in operation due to the heat generated when the coal is burned.

0006Furthermore, pipes in a chemical plant or refinery, for example, that carry fluids that are hotter or colder than ambient conditions, are subject to cycles of heating and cooling, and the associated changes in length that such cycles occasion. These piping networks typically require multiple expansion joints or loops to avoid over-stressing the pipes due to expansion and contraction, especially for long pipe runs. Pipes joined by flexible couplings readily accommodate the deflections due to thermal expansion and contraction and thereby eliminate the need for special expansion joints or loops in the network.

0007Piping networks may also be subject to significant motion, for example, when built over seismically active regions of the earth. Deflections of pipes during tremors and minor earthquakes may be accommodated by flexible couplings that maintain the fluid integrity of the joints.

0008There is clearly a need for pipe couplings which provide a degree of flexibility to the joints of a piping network that will enable the network to be assembled in the field, according to design, without maintaining close tolerances or the need for modifications that deviate from the plan substantially, and accommodate thermal expansion and contraction as well as other deflections without compromising the integrity of the joints.

SUMMARY OF THE INVENTION

0009The invention concerns a coupling assembly for flexibly and sealingly joining pipes to one another end to end and permitting axial, angular and torsional deflections between them. The coupling assembly comprises a first ring attachable to one of the pipe ends. The first ring has an outer diameter greater than the pipe and an outwardly facing circumferential groove. A first sealing member is positionable within the groove of the first ring. The first sealing member extends circumferentially around the first ring. A second ring is attachable to another of the pipe ends to be joined. The second ring has an outer diameter greater than the pipe and an outwardly facing circumferential groove. A second sealing member is positionable within the groove of the second ring and extends circumferentially around the second ring. A band is positionable in overlying relation with and surrounding the first and second rings. The band has an inwardly facing surface sealingly engageable with the first and second sealing members. A housing is positionable in overlying relation with and surrounding the rings and the band. The housing is radially spaced apart from the band allowing the band to float on the sealing members. The housing has a pair of circumferential rims positioned in longitudinally spaced apart relation to one another. Each rim is sized and toleranced to maintain the aforementioned spaced relation between the housing and the band. The housing also has a pair shoulders positioned in spaced apart relation and facing one another. Each shoulder is engageable with one of the rings for limiting axial and angular deflection of one pipe relative to the other.

0010The invention also includes a method of sealingly and flexibly attaching pipes to one another end to end. The method comprises the steps of:

0011(A) attaching a first ring to one pipe end, the first ring having an outwardly facing circumferential groove therein;

0012(B) attaching a second ring to another pipe end, the second ring also having an outwardly facing circumferential groove therein;

0013(C) inserting the first ring through a circumferentially extending band such that the band does not overlie the circumferential groove in the ring;

0014(D) positioning a first sealing member within the groove of the first ring;

0015(E) positioning a second sealing member within the groove of the second ring;

0016(F) bringing the first and second rings adjacent to one another in co-axial alignment;

0017(G) sliding the band circumferentially around the rings, the band having an inwardly facing surface sealingly engaging the first and second sealing members; and

0018(H) positioning a housing circumferentially around and in spaced relation to the band and the rings, the housing having shoulders in spaced relation and facing one another, the shoulders being engageable with the rings to limit axial and angular deflection of the pipes relative to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

0019<figref idref="DRAWINGS">FIG. 1</figref> is an end view of a coupling according to the invention;

0020<figref idref="DRAWINGS">FIG. 2</figref> is a side view of the coupling shown in <figref idref="DRAWINGS">FIG. 1</figref>;

0021<figref idref="DRAWINGS">FIG. 3</figref> is an end view of another embodiment of the coupling according to the invention;

0022<figref idref="DRAWINGS">FIG. 4</figref> is a cross-sectional view of the coupling taken at line <b>4</b>—<b>4</b> of <figref idref="DRAWINGS">FIG. 1</figref>;

0023<figref idref="DRAWINGS">FIG. 4A</figref> is a cross-sectional view of another embodiment of the coupling according to the invention;

0024<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional view of the coupling illustrating angular displacements of the pipe ends permitted by the coupling according to the invention; and

0025<figref idref="DRAWINGS">FIG. 6</figref> is an exploded view of the pipe coupling assembly according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

0026<figref idref="DRAWINGS">FIGS. 1 and 2</figref> show the mechanical pipe coupling <b>10</b> according to the invention. Preferably, the coupling <b>10</b> has a housing <b>12</b> formed of a plurality of housing portions <b>14</b> and <b>16</b> attached to one another end to end to surround and engage the ends of pipes <b>18</b> and <b>20</b>, shown in phantom line. The housing portions <b>14</b> and <b>16</b> are attached to each other using fasteners such as bolts <b>22</b> and nuts <b>24</b> that bear against lugs <b>26</b> and <b>27</b> that extend outwardly from each housing portion <b>14</b> and <b>16</b> respectively. The fasteners <b>22</b>, <b>24</b> clamp the lugs <b>26</b> and <b>27</b> to one another in what is called “pad-to-pad engagement” to hold the housing portions end to end around the pipes <b>18</b> and <b>20</b>. The bolted attachment is advantageous because it allows the coupling to be easily disassembled for repair or modification. <figref idref="DRAWINGS">FIG. 3</figref> illustrates an alternate embodiment of the housing <b>12</b> having four housing portions <b>14</b><i>a</i>, <b>14</b><i>b</i>, <b>16</b><i>a </i>and <b>16</b><i>b </i>attached end to end by fasteners <b>22</b>, <b>24</b>.

0027<figref idref="DRAWINGS">FIG. 4</figref> shows the coupling <b>10</b> in cross section. Housing portions <b>14</b> and <b>16</b> each have a pair of rims <b>28</b> positioned in longitudinally spaced apart relation to one another lengthwise along the housing <b>12</b>. Rims <b>28</b> extend radially inwardly and are sized and held to tolerances so as to maintain a separation <b>29</b> between themselves and the pipes <b>18</b> and <b>20</b>. The separation <b>29</b> is made possible by the pad-to-pad engagement of lugs <b>26</b> and <b>27</b> which holds the rims <b>28</b> at a diameter slightly greater than the outer diameter of pipes <b>18</b> and <b>20</b> and thereby permits relative axial, torsional and angular deflections between the pipes. Preferably the radial faces <b>31</b> of rims <b>28</b> are angled outwardly so as to further facilitate angular pipe deflections. The rims <b>28</b> are also sized so that, during any deflection between the pipes, contact that does occur between the housing portions <b>14</b> and <b>16</b> and the pipes <b>18</b> and <b>20</b> is made between the rims <b>28</b> and the pipes, and not between other portions of the housing <b>12</b> and other components comprising the coupling <b>10</b> as described below.

0028Each housing portion <b>14</b> and <b>16</b> also has a pair of shoulders <b>30</b>, also positioned in longitudinally spaced apart relation to one another. Shoulders <b>30</b> face each other and engage other components of the coupling to limit axial and angular displacement of the pipes <b>18</b> and <b>20</b> as described below.

0029As further shown in <figref idref="DRAWINGS">FIG. 4</figref>, each pipe <b>18</b> and <b>20</b> has a respective ring <b>32</b> and <b>34</b> attached at or near its end. Rings <b>32</b> and <b>34</b> are preferably co-axially mounted on the pipe ends <b>18</b> and <b>20</b> and held in place by welds <b>36</b>. Alternatively, as shown in <figref idref="DRAWINGS">FIG. 4A</figref>, rings <b>32</b> and <b>34</b> may be butt welded to the ends of the pipes <b>18</b> and <b>20</b>. Referring again to <figref idref="DRAWINGS">FIG. 4</figref>, rings <b>32</b> and <b>34</b> have larger outer diameters than the pipes <b>18</b> and <b>20</b> to which they are attached and engage the shoulders <b>30</b> on housing portions <b>14</b> and <b>16</b>. The housing portions <b>14</b> and <b>16</b> have sufficient length <b>38</b> between shoulders <b>30</b> to accommodate the rings <b>32</b> and <b>34</b> with a gap <b>40</b> between the ends of pipes <b>18</b> and <b>20</b>. Gap <b>40</b> allows for axial deflection of the pipes <b>18</b> and <b>20</b> relative to one another, and the engagement of the rings <b>32</b> and <b>34</b> with shoulders <b>30</b> limits the range of this deflection and holds the ends of pipes <b>18</b> and <b>20</b> within the housing <b>12</b>. As shown in <figref idref="DRAWINGS">FIG. 5</figref>, the relative deflection of the pipes <b>18</b> and <b>20</b> can manifest itself in an angular displacement <b>42</b> between them. This occurs when one side of the pipe moves outwardly toward the shoulder <b>30</b> while the opposite side of the pipe moves inwardly away from the shoulder. It is preferred to size the rings <b>32</b> and <b>34</b> and the spacing between the shoulders <b>30</b> so as to limit the maximum angular deflection <b>42</b> to between 2° and 4° depending upon the application to which the piping network is dedicated. This preferred range of angular displacement, along with the permitted axial and torsional deflections, ensure that the joints created by the coupling <b>10</b> are flexible enough to compensate for motion of the piping network due to thermally related expansion and contraction, motion induced by limited seismic activity, as well as to compensate for the typical tolerances encountered during network fabrication, and yet are not too flexible so as to compromise the fluid integrity of the joints formed by the couplings.

0030As shown in <figref idref="DRAWINGS">FIGS. 4 and 5</figref>, each ring <b>32</b> and <b>34</b> has an outwardly facing circumferential groove <b>44</b> that receives a sealing member, such as an O-ring <b>46</b>. To effect a seal that is independent of the housing <b>12</b>, a band <b>48</b> is positioned in spaced relation radially away from housing portions <b>14</b> and <b>16</b>. Band <b>48</b> surrounds the rings <b>32</b> and <b>34</b> and has an inwardly facing surface <b>50</b> that sealingly engages the O-rings <b>46</b> to effect a fluid tight seal around the ends of pipes <b>18</b> and <b>20</b>. The pad-to-pad engagement of lugs <b>26</b> and <b>27</b> ensures that a radial separation <b>52</b> is maintained between the band <b>48</b> and the housing portions <b>14</b> and <b>16</b>. Radial separation <b>52</b> allows band <b>48</b> to float on the O-rings <b>46</b> and maintain concentricity with the pipes <b>18</b> and <b>20</b>. By remaining substantially concentric, band <b>48</b> maintains substantially equal pressure circumferentially around the O-rings <b>46</b> and thus ensures a fluid tight seal at the joint formed by coupling <b>10</b> despite the permitted axial and angular displacement of pipes <b>18</b> and <b>20</b>. Housing portions <b>14</b> and <b>16</b> have a second pair of shoulders <b>33</b>. Shoulders <b>33</b> are positioned on opposite sides of band <b>48</b> to engage the band edges and help maintain its engagement with O-rings <b>46</b> to ensure the fluid tightness of the joint. The separation <b>29</b> between rims <b>28</b> and pipes <b>18</b> and <b>20</b> is controlled relative to the radial separation <b>52</b> between housing portions <b>14</b> and <b>16</b> and band <b>48</b> such that if contact occurs, it occurs first between the rims <b>28</b> and the pipes <b>18</b> and <b>20</b>, thereby preventing further contact between the housing portions <b>14</b> and <b>16</b> and band <b>48</b>.

0031Assembly of the coupling <b>10</b> according to the invention is illustrated in <figref idref="DRAWINGS">FIG. 6</figref>. Rings <b>32</b> and <b>34</b> are welded onto ends of pipes <b>18</b> and <b>20</b>, respectively. Next the ring <b>32</b> is passed through the band <b>48</b>, the band being positioned such that it does not overlie the circumferential groove <b>44</b>. O-ring sealing members <b>46</b> are then positioned within grooves <b>44</b>, and the pipes <b>18</b> and <b>20</b> are positioned adjacent to one another in coaxial alignment. Band <b>48</b> is then drawn from ring <b>32</b> toward ring <b>34</b>, the inwardly facing surface <b>50</b> sealingly engaging the O-rings <b>46</b> on each ring. Housing portions <b>14</b> and <b>16</b> are next positioned around band <b>48</b> and rings <b>32</b> and <b>34</b> and attached to one another end to end using bolts <b>22</b> and nuts <b>24</b> to bring lugs <b>26</b> and <b>27</b> into pad-to-pad engagement.

0032Flexible pipe couplings according to the invention allow piping networks to be assembled that are sufficiently flexible to accommodate significant thermally induced deflections, motion due to seismic forces as well as deviations in dimensions due to accumulation of tolerance errors without compromising the integrity of the joints formed between the pipe segments.